1. Field of the Invention
The invention relates generally to physical vapor deposition (PVD) of metal films. The invention relates more specifically to DC magnetron sputtering of metals such as aluminum (Al) or aluminum alloys onto semiconductor substrates and the like for forming fine pitch metallization such as the electrically-conductive interconnect layers of modern integrated circuits.
2. Cross Reference to Related Patents
The following U.S. patent(s) is/are assigned to the assignee of the present application, and its/their disclosures is/are incorporated herein by reference:
(A) U.S. Pat. No. 5,242,566 issued Sep. 7, 1993 to N. Parker; and
(B) U.S. Pat. No. 5,320,728 issued Jun. 14, 1994 to A. Tepman.
3. Description of the Related Art
The electrically-conductive interconnect layers of modern integrated circuits (IC) are generally of very fine pitch (e.g., 10 microns or less) and high density (e.g., hundreds of lines per square millimeter).
A single, small defect in the precursor metal film that ultimately forms a metallic interconnect layer of an IC can be so positioned as to seriously damage the operational integrity of the IC. As such it is desirable to form metal films with no defects or as few, minimally sized defects as possible.
The metal films of integrated circuits are typically formed by physical vapor deposition (PVD). One low cost approach uses a DC magnetron apparatus such as the Endura.TM. system available from Applied Materials Inc. of California for sputtering aluminum (Al) or aluminum alloys onto semiconductor wafers.
Although such DC.sub.-- magnetron PVD systems generally produce high quality metal films with relatively low defect densities, heretofore unexplained `blobs` of extra material are occasionally observed in the deposited metal. These blobs can interfere with device formation and disadvantageously reduce mass production yield of operable devices.
The present inventors have isolated such blobs in DC.sub.-- magnetron-formed aluminum films, have analyzed the composition and physical structures of such blobs, and have developed methods for minimizing the formation of such undesirable blobs.